The present invention relates to a power-generating plant which utilizes, as a working fluid, a gaseous low-boiling point medium produced by the direct contact of the low-boiling point medium with a heat-source medium. More specifically, the invention relates to a power-generating plant in which the circulating force of the working fluid is increased.
A power-generating plant consists chiefly of an evaporator unit for producing a working fluid, a turbine unit for converting the thermal energy of the gaseous working fluid produced in the evaporator unit into an electric energy, and a condenser unit for liquefying the working fluid which has done the work in the turbine. The working fluid circulates in a closed cycle formed by connecting the above-noted units.
In recent years, a low-boiling point medium has been widely used as a working fluid for power-generating plant in order to efficiently utilize natural resources. For example, a low-boiling point medium such as freon, butane, ammonia or the like is used as a working fluid, and is vaporized by exchanging the heat with a heat-source mdium which is heated, such as hindered ester oil, turbine oil, alkylbenzene oil or the like. Usually, however, these low-boiling point media have small heat conductivity presenting great thermal resistance at the time of vaporization. Therefore, when the heat is to be exchanged by bringing the low-boiling medium into indirect contact with the heat-source medium, the areas for conducting the heat must be increased. This causes the heat exchangers to become bulky which is economically disadvantageous from the standpoint of the whole power generating plant. It is therefore required to reduce the size of the heat exchangers.
A heat exchanger of the direct contact type for heating a low-boiling point medium that serves as a working fluid has been proposed in, for example, Japanese Patent Laid-Open No. 52-118146 filed in 1976, wherein the point medium is brought into direct contact with a heat-source medium. According to this publication, either one of the low-boiling point medium or the heat-source medium is introduced into a lower portion of the heat exchanger, and the other liquid is introduced into an upper portion of the heat exchanger, such that the two liquids will flow in the opposite directions in the heat exchanger. However, when the two liquids are caused to flow in the opposite directions in the heat exchanger as proposed in this publication, the two liquids collide whereby a circulating force of the heat-source medium is weakened in the heat exchanger and in the closed cycle including the heat exchanger. Consequently, the heat exchanger cannot sufficiently increase its heat-exchanging performance, and the turbine cannot increase its operation efficiency. Further, in order to increase the circulating force of the heat-source medium, a pump, installed in the closed cycle of heat-source medium, must have increased capacity.